In Head Over Tail
by Supervillegirl
Summary: (Or 4 Times John's Tail Was a Problem & 1 Time It Wasn't) The second in my Tail series. A fun collection of John's merman-ness interfering with his life.


**One**

"John!" Sherlock Holmes yelled out in warning as he raced along Lambeth Bridge, Detective Inspector Greg Lestrade right behind him.

John was struggling with the suspect, who had gotten the jump on him, and they were right at the edge of the railing. If they went over… Sure, it was night, so no one would see John when he transformed, but how would Sherlock explain his disappearance? How would he stop them from performing search and rescue operations?

Well, he better think of something quick, because just then, the suspect popped John in the jaw and used his shoulder to ram John into the railing. John hit the railing, and his momentum shoved him over it and down towards the Thames. The suspect took off towards Horseferry Road, and Sherlock rushed to the railing where John had disappeared, peering through the dark to try and see anything.

"Where is he?" demanded Lestrade, running up next to Sherlock and looking down into the water as several officers went after the suspect.

Sherlock quickly calculated where John would have fallen and how fast the current was moving and zeroed in on a point roughly thirty feet away from the bridge. He could vaguely see what appeared to be a large, dark merman's tail fin breach the surface of the river and then disappear into it. He then glanced down under the bridge to see that the tide had lowered and there was a small amount of shore there.

Thinking fast, Sherlock turned to Lestrade. "John's a soldier. He would most likely survive that fall and swim to shore further downstream. You take the south bank, I'll take the north."

Lestrade nodded and ran down the bridge towards the south side of the Thames. Sherlock turned and ran towards Horseferry Road, glancing up towards Lestrade before making his way down to the riverside, where the tide had lowered to reveal about five feet of wet sand and silt next to the north wall of the river. Sherlock glanced around to see if any boats were close or pedestrians were looking under the dark bridge—thank God he wore dark colors—before approaching the water.

After a few seconds, John poked his head and bare shoulders up through the surface of the water about five feet in front of him. "Is it safe?"

"Yes," Sherlock told him, stepping forward until his shoes reached the edge of the lapping water.

John pushed forward through the shallow water, dragging his body behind him. When he got close enough, he raised his hands, and Sherlock grabbed hold of them and dragged his friend to the shore. John turned over onto his back as Sherlock moved down to haul John's tail over so that it was out of the water.

"Where's the Yard?" John asked as he held his hand over his tail and started drying the water from himself and the ground underneath him.

"Half chasing the suspect, half search and rescue," Sherlock answered.

John looked up at him in alarm.

Sherlock pointed downriver. "I sent Lestrade to search further down the south bank while I search the north. Imagine his surprise when I turn up with you, none the worse for wear."

John relaxed as he went back to drying himself off. "How are we going to explain that?"

"Are you able to make it _look_ like your hair and clothes are wet?" asked Sherlock.

"Yeah," said John.

"Then I have a plan," Sherlock told him.

Just then, John's form was enveloped by the column of water that always accompanied his transformations, and then he was back, legs, clothes and all.

John pushed himself up onto his feet. "What is it?"

Sherlock stepped over to the water. "Start that forcefield effect you use when it's raining." He bent down and cupped his hands in the river.

"All right," John told him. "Ready."

Sherlock turned slightly and—feeling a bit ludicrous—flung water up at his friend several times until his head and his clothes had a good layer of water on them. At least, it looked like they were wet. In fact, the clothes probably were; John was probably only keeping the water off his skin.

Sherlock stood up, patting his hands dry on his coat and then removing it to drape over John's shoulders. John grasped the edges of it and wrapped it around himself like a blanket.

"You look a bit ridiculous, there," said John, pointing at Sherlock's throat.

Sherlock looked down at the scarf knotted at his throat, sticking out like a sore thumb without the Belstaff to accompany it. "I do. Here, take it." He pulled the scarf off and tucked it around John's neck under the coat collar.

The coat fell practically to John's shoes and, frankly, it reminded Sherlock of a child trying on his father's clothes.

"Perfect, you look just like you almost drowned," said Sherlock, setting off back up to the street as he ignored John's grumblings.

* * *

 **Two**

John groaned at his flatmate. "Haven't you done enough tests?"

Sherlock arranged his notes on the table. "And now, I'm bored."

John rolled his eyes.

"You should be grateful, John," Sherlock told him. "When I first learned your secret, I came up with a considerable list of experiments to run. Instead of springing them on you all at once, I decided to save most of them for when I'm bored."

"Oh, well, in that case," grumbled John, turning away.

"Oh, relax," said Sherlock. "It's not as though I'm asking you to strip so I can see exactly how you transform."

John looked over at him with a mildly horrified frown. "That wasn't ever on the list, was it?"

Sherlock hesitated, his eyes moving to the floor. "Thought up and then immediately discarded before making it onto the list."

John stared at his friend's notes and then grimaced. "Fine."

Sherlock's eyes lit up as John walked further into the sitting room. "Excellent! Start by moving that pillow there with your mind."

It was twenty minutes later as John was levitating the coffee table, the skull, Sherlock's violin and the microscope simultaneously that there was a knock on the door and it began opening.

"Ooh-hoo!"

John immediately moved the microscope towards the kitchen and the violin and skull to the couch—each of them landing with a light thud—but there wasn't any time to put the table back down without Mrs. Hudson seeing. Instead, he pushed the table towards the ceiling, pinning it there. He then moved the hand keeping it there behind his back.

Mrs. Hudson swung the door open and smiled at them. "Oh, good. Sherlock, you've got a client downstairs."

Sherlock frowned as he glanced past her. "Why didn't you bring them up?"

"He refused to come in," Mrs. Hudson told him. She glanced down at the sofa, stepping forward and picking up the skull. "He seemed a bit odd." She turned, looking down at the floor in front of the sofa. "What'd you boys do with the table?"

"One of the legs broke," Sherlock told her. "We took it to get repaired."

John glanced nervously up at the floating table above them.

Mrs. Hudson's brows drew together as she started towards the fireplace. "I'm happy for the two of you, but couldn't you keep that stuff in the bedroom?"

"No, no, no, Mrs. Hudson," John quickly told her, his eyes wide. "That's not what's happening— **at all**. I ran into it last night, and I guess the leg was cracked enough from _someone_ stepping on it all the time that it broke."

Mrs. Hudson placed the skull in its usual spot at the mantelpiece. "You don't need to spare my sensibilities. I was a bit of a wild one when I was young, too."

John looked over at Sherlock, giving him an exasperated look. Sherlock just glanced up at the floating table and back to John with a question in his gaze. John nodded to show he was doing all right.

Mrs. Hudson turned from the fireplace and spotted the microscope on the kitchen floor. "Oh, boys…"

John rolled his eyes and made to turn away but then turned back as he remembered that the hand working to keep the table floating was behind his back.

Mrs. Hudson set the microscope on the table and turned to leave. "Please hurry. I don't want that man standing on my doorstep all day." She then left through the kitchen door and headed down the stairs.

John let out a tense breath as he let the coffee table float back to the floor.

"No, you have to put it in one of our rooms," Sherlock told him. "She thinks it's being fixed, and she never goes in the bedrooms."

"Right," muttered John as he set off to put the table in Sherlock's room. After all, it wasn't like he used it that much.

* * *

 **Three**

"The suspect attends an elite club, only accessible to shoe with prestigious medical professions," Sherlock explained. "The best place to get him to talk would be somewhere that he is relaxed, probably the sauna. But he needs to believe the person he is talking to is a real doctor. Therefore, the person we send in undercover needs experienced medical knowledge. John."

John froze on the spot, hoping he didn't look as scared as he thought he did. No one else seemed to think so, as they simply glanced at John and then back to the plans on the conference table in front of them. Sherlock, however, never missed anything. Sherlock frowned at whatever micro-expression John was giving off, reading who knew how many clues in the clench of his fists, the way he was standing and whatever else he was deducing. All of this happened in the split second it took for the officers to look down at the table, and then, Sherlock was talking again.

"Wait, John, weren't you telling me you had to take antibiotics for a few weeks?"

Catching onto what Sherlock was implying, John responded, "Yeah, I'm taking antibiotics."

"You're sick?" asked Lestrade.

"Just a little tonsillitis," John told him, thinking quickly. "But antibiotics have the potential to cause kidney problems, and saunas can cause dehydration, so…"

"I can do it," Anderson volunteered.

"Don't be ridiculous," Sherlock muttered, pulling his phone out. "Your improvisational skills are appalling. Mike Stamford it is."

Anderson's jaw clenched as he glanced over at Donovan, and they shared a mutual, hateful glare.

Sherlock finished typing out his text, and he tucked his phone back away. "There's his number. Feel free to give him a call. He'll be more than cooperative. John."

Sherlock strode to the door as Lestrade pulled out his phone to look at the text. John followed his friend out towards the lifts, and after a moment, they stepped into the car and the doors closed.

"You can't do saunas?" asked Sherlock in curiosity.

"No," John told him. "I mean, steam is still water, but it has less substance than water, so it's harder to control. I can't really explain it."

"No problem," said Sherlock. "You can search elsewhere on the premises for clues."

"What, instead of you?" asked John, looking at him in surprise.

"Like I said, you have the medical knowledge," Sherlock told him. "If you get stopped, you can blend in better."

* * *

"Blend in better," muttered John in irritation as he frantically tried to towel off his tail. "Yeah, right."

John had been doing just fine snooping through the club in the best suit he owned until he had been passing through a corridor and the sauna door had opened for a man exiting it, sending a cloud of steam into John's face.

"Oh, sorry, mate," the robe-clad man had said as he closed the door behind him.

"No worries," John had replied as he turned and quickly walked towards the nearest door he could find: the showers.

He had gotten the door closed behind him—and thankfully, the room had been empty—just as his legs vanished from under him. Everything would have been fine; he would have used his heating power to dry himself and the floor around him off. The problem had started when one of the pipes in a corner had begun to leak and run towards the drain in the middle of the room, right where John lay. John had frozen the leak into a sleeve of ice around the pipe, but it had then burst and started spraying onto the floor, flooding it. John had been unable to keep up with that much water.

And now, here he was, towels from the cabinet in the corner shoved under him and two towels in hand, trying desperately to dry himself off before someone came along.

John heard the doorknob turn, and he flung his arm out towards the door as it started to open. The door slammed shut with a bang, and John turned the doorknob and latch into a big block of ice, freezing them to the doorjamb. The knob jiggled slightly, and someone started knocking on it.

"Hey, what happened in there?" the man on the other side of the door called.

 _Oh, what now?_ John wondered as he began to panic.

* * *

Sherlock frowned as he leaned closer to the monitor. The surveillance cameras the Yard had set up in the club were positioned in the high-traffic areas, and one of those areas was the corridor in the spa area outside the sauna. On the monitor, men were starting to congregate in front of the door to the showers, trying to open it, but it wouldn't budge.

 _Strange,_ Sherlock thought. _That door doesn't lock._

As one man moved around to the other side of the door—and thus moving out of the way of the camera's view of the door—Sherlock spotted a water puddle slowly emerging from under the door.

Sherlock's eyes widened as he unconsciously calculated the amount of time it would take to get from the sauna door and into the shower room: approximately seven seconds. _John._

Sherlock glanced over at the officers gathered at the other end of the table. He quickly typed on the keyboard, cutting off the feed to a few of the cameras, and then he snuck out of the room. After securing a maintenance uniform, he made his way to the corridor, where club members were now shoving their shoulders into the door to try and open it.

"Oh, has that door locked itself again?" Sherlock called, throwing on a Yorkshire accent. He approached the group as they turned to look at him. "It's been a constant pain in the arse since they installed it."

"Why are the showers locked?" one man asked. "They're showers."

"New security feature," Sherlock answered, making his way through them and fumbling for the ring of keys on his belt. "With all the criminal activity going on lately, I guess they wanted somewhere for people to lock themselves in if a crazy gunman showed up. Let me just…" He pulled the keys from his belt and looked down at them to sort through them and then let his eyes fall on the water trickling out from under the door. "Oh, bugger. It looks like a pipe burst. I'm gonna need you fellas to clear the corridor until I get it patched."

"I think someone's in there," one man told him as the others moved off. "I think he fell against it when I tried to get in there, but he hasn't responded."

"Right, ta," said Sherlock, turning towards the door and sifting through the keys on the ring while the man left. Once he had turned the corner, Sherlock leaned close to the door. "Coast is clear."

Steam rose slightly from the crack between the doorknob and the latch and then stopped. Sherlock waited a moment and then cracked open the door enough to enter and close it behind him.

John lay on the tiled floor in all his merman glory on top of some towels, which were soaked through as the busted pipe spilled water over the floor. "Thank God." He tossed another wet towel aside with a wet _SMACK!_ "I thought they were about to get through the door."

"What happened?" asked Sherlock as he took the discarded towel and placed it underneath the pipe.

"Someone came out of the sauna just as I walked past," John explained as Sherlock walked back over to him. "I can't dry off in here; there's too much water."

"I have a plan," said Sherlock. "Move." He grabbed hold of the towels under John's tail and pulled them out as John dragged himself back onto the tiled floor.

* * *

Sherlock opened the door that led to the pool, glancing around before turning and dragging John towards the pool.

"You're sure the camera isn't working?" John asked.

"Yes," Sherlock told him in a strained voice as he pulled on John's hands to get him to the edge of the pool.

"And you're sure Mike is close to getting a confession?" John asked. "'Cause I'm not sure how long I can—"

Sherlock stopped to look down at him. "John, do you really think I haven't already thought of all this?"

"Right, sorry," muttered John.

Sherlock reached the edge of the pool, and John pushed himself off of the edge into the water. Oh, it was like a breath of fresh air. Despite the concern he still felt about his predicament, there was a certain joy that always came from behind in the water. John took a quick lap of the pool before surfacing next to Sherlock.

"Just stay invisible if anyone comes in," Sherlock told him. "Pretty soon, everyone will be focused on arresting Michaels, and we'll be able to dry you off then. I'll stay in the room pretending to fix things should I need to clear people out who have been here too long."

John nodded and took off back through the water, entertaining himself with swimming to pass the time. Sherlock watched the smooth way he moved through the water, the blue and white tail pumping powerfully to push him along. He felt a brief moment of jealousy at the fact that he wasn't able to experience it as well.

"Brilliant," Sherlock muttered before turning and pretending to be fiddling with some pipes by the door.

* * *

 **Four**

John finished wiping his nose with a tissue before throwing it in a rubbish bin as he passed. "Are you sure I should be tagging along?" he asked in a slightly nasal tone through his congestion. "I could contaminate the crime scene."

"Nonsense," Sherlock brushed off. "You're a doctor. You know how best not to spread disease. Although, I did mention that you didn't have to come."

"Oh, I'm sick of staring at my bedroom ceiling, "John told him, using another tissue to blow his nose.

"I thought doctors loved to prescribe bed rest," Sherlock pointed out with an annoyed tone.

"Not all doctors used to be soldiers," John grumbled as he used the bottle of hand sanitizer in his coat pocket to clean his hands. "I can only handle so much downtime."

Sherlock smirked. "Careful. You're starting to sound like me."

"Oh, God forbid," John said in a horrified tone before laughing, which then turned into a slight coughing fit.

They rounded the corner onto Chelsea Bridge Road and approached the crime scene, Sherlock brushing through Anderson and Donovan as usual. It didn't seem all that unusual of a case—a man who had been shot to death—until Sherlock was in the middle of his examination of the body.

John felt that tickle that preceded a sneeze, and he scrambled to get a tissue out of his pocket, sneezing into it.

"Bless you," Lestrade told him.

"Ta," John said, wiping at his nose and pocketing the tissue.

"I can't believe he dragged you out of bed," Lestrade went on.

"Believe it or not, I asked to come," John replied. "I've been in bed for almost three days straight." He cleaned his hands with sanitizer as Sherlock moved to another vantage point around the body.

Lestrade chuckled as he raised his coffee to his lips. "Careful. You're—"

"—starting to sound like him," John joined in. "Yeah, I know."

Lestrade started to take a drink of his coffee, but then he frowned and looked down into the cup. "What the—"

John looked over at him as Lestrade turned the cup upside down.

Starting to get a bad feeling, John asked, "What?"

Lestrade turned the cup to show John that the coffee was completely frozen solid.

 _Oh, dammit,_ John thought as he gave a frown. "How'd it freeze? It's not even that cold out."

"Never seen that before," said Lestrade, staring down into his cup.

John glanced over at Sherlock, his heart starting to pound. "You found anything yet, Sherlock?"

Sherlock stood up. "A bit. John."

Recognizing his friend's request for a medical examination, John nearly swore under his breath as his mind raced at a million miles a minute.

 _Oh, shit, oh, shit, oh, shit, oh, shit…_

John moved forward, determined to not breathe heavily enough to cause a sneeze. But, of course, once you tried to suppress sneezing or couching, that's when it became that much harder to do.

He knelt down next to the body, trying to touch it as little as possible so as not to contaminate it. It wasn't long, though, before he felt another sneeze coming on.

 _No,_ he thought in a panic as he brought his hand to his nose. _Not now with everyone watching. Don't breathe, don't breathe—_

John backed away from the body about a foot before he sneezed. Instantly, a frost crept quickly over the ground in front of him, the damp pavement freezing over. John's eyes widened as he looked up at Sherlock, who was staring back at him with wide eyes.

"Wait a minute," said Lestrade, moving forward to see around John.

John immediately turned his hand, clenching the fist to cause the frost to melt.

"Did I just see…" Lestrade trailed off as he moved to John's side and looked down at the normal, damp pavement.

Sherlock looked down at the body and back up at Lestrade in expectation. "Did you see what?"

Lestrade shook his head. "Nothing. I guess I'm tired."

"Then why did you say anything?" Sherlock demanded in an annoyed tone. "This man was not killed by a gunshot. He was stabbed."

"But there are no stab wounds on the body," Lestrade pointed out.

"There is." Sherlock directed his gaze to the gunshot wound in the man's gut.

"That's a gunshot wound," said Lestrade. He gestured with the hand holding his frozen coffee. "You can see the powder burns on his shirt."

"But there are no powder burns on his hands," Sherlock replied.

Lestrade could only frown at him.

Sherlock gave an exaggerated eye roll. "If someone were holding a gun to _your_ stomach, wouldn't you grab for it? Conclusion: this man was either unconscious or already dead when he was shot. There are no injuries to his head, so it was the latter."

John felt that tickle again, and he threw his hand to his nose, trying to stifle it.

"Now, why would you shoot a dead man, especially with the gun pressed up against his skin?" Sherlock went on. "The suspect was trying to get the bullet into that specific spot to make it look like a gunshot. He was trying to cover something up."

Unable to hold it in any longer but trying his hardest to rein in his powers, John let out another sneeze.

Sherlock turned towards the street to leave, speaking quickly. "Take the body to Bart's and do an autopsy; you'll find some piece of the blade that killed him, and it'll be distinctive in some way that will lead you to the killer."

John glanced over at Lestrade, who was looking down at his now steaming coffee, a deep frown on his face. He turned and hurried after Sherlock, catching up as he finished blowing his nose.

"What was that?" Sherlock asked.

"Colds and flus can affect my powers," John explained.

"Then why did you leave the flat?" Sherlock demanded as they approached Royal Hospital Road.

"It hadn't happened in years," John told him. "I'd gotten so good at controlling my powers when I was sick. This must be a really bad bug to set them off again."

"So, back to isolation in the flat," said Sherlock.

"Oh, God," grumbled John as another sneeze came on, causing the oil in a deep fryer of a churro vendor's cart to burst into flames. As they hurried away form the scene, Sherlock's laughter rang out into the night.

* * *

 **Five**

Sherlock watched as the suspect dashed into Criterion Theatre, and he turned his head to yell back to John behind him, "Cut him off around back!" He ran through the lobby doors and past the bewildered box office clerk, chasing after the man.

The suspect led him through the empty theatre and backstage, down the stairs and into the storage and dressing room hallways in the basement. It was when Sherlock rounded the second corner that he was brought up short. The suspect stood in the corridor, two other men behind him, one behind the other. Apparently, they had entered through another door.

Sherlock brought himself to a sudden stop, smirking. "So, you _do_ have accomplices. I knew it."

"Where's Dr. Watson?" his suspect asked.

Sherlock forced himself into a confused frown and turned to look behind him. He gave a disappointed sigh and turned back. "He never can keep up. Probably lost upstairs."

 _Come on, John,_ he thought. _Any moment now would be good._

"What evidence do you have on me?" asked the man.

"Oh, I have plenty," Sherlock told him, biding for time.

"Where?" asked the man.

"Do you really think I'm stupid enough to tell you?" said Sherlock. "That evidence is my leverage. I give that up, I'm dead."

A flicker of movement caught his attention, and Sherlock looked past the three men to where a set of curtains was hung at the end of the hall, pulled to a hook on each side to frame the entryway there. The tassels on the edge of the curtain were swaying as though someone had just brushed past them.

 _Oh, John, you brilliant man,_ he thought.

"You'll be dead if you don't," said the suspect.

"If I hand over my evidence, the only remaining evidence against you is me, so you'll kill me," Sherlock replied. "And if you kill me now, you'll never get the evidence. A rather empty threat, yes?"

The man at the back of the corridor suddenly jerked as though hit over the head, and then he crumpled, his unconscious descent halted in midair halfway to the floor. His body was then slowly lowered to the floor.

The suspect pulled out a gun and aimed it at Sherlock. "Considering you're probably the only one who knows where this evidence is, killing you would still take care of the problem, wouldn't it?"

Sherlock gave a dramatic gasp, widening his eyes. "Oh, dear. You caught me. I never even thought of that."

The suspect rolled his eyes. "Let me guess: in the evet of your death, the evidence gets released to the authorities."

"Naturally," said Sherlock as the second accomplice was dispatched by the invisible foe.

"And something tells me you can't be bribed," said the suspect.

"Not even a little," said Sherlock. "What a pickle you seem to be in. You haven't even noticed that your backup has been taken out."

The suspect frowned and turned his head to see the two unconscious men on the floor. He turned on the spot, eyes scanning the empty hallway, and then turned back to Sherlock, the gun aimed at his head. "What did you do?!"

"I've been standing in front of you the whole time," Sherlock stated like he was stupid. "I'm not _that_ good." His gaze shifted to just over the man's shoulder as John seemed to materialize out of thin air. "He, however, is."

The suspect turned as John grabbed his gun hand and pointed it up towards the ceiling. The gun went off once, the bullet lodging harmlessly in the wooden beams above them. John rammed his elbow into the man's ribs, which loosened his hold on the pistol, and John yanked it from his hands and used it to whack him across the face. The suspect crumpled to the floor, unconscious.

Sherlock pulled his mobile phone out, typing out a text to Lestrade. "We should take care of criminals like this more often."

"Well, there's usually other people watching, so, no thanks," muttered John, keeping the gun trained on the three men, should one of them rouse. He glanced back at the detective. "Did you really have the evidence ready to go to the police if he killed you?"

"Of course not," Sherlock told him. "I didn't even _have_ evidence."

John shook his head as he laughed.


End file.
